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Chemistry (Inorganic) > Group 7 > Flashcards

Group 7 Flashcards

1
Q

Describe the trend in reducing abilities of halide ions

A

Reducing ability increases down the group

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2
Q

Explain the trend in reducing abilities of halide ions

A

Reducing ability increases down the group
- Ionic size increases down the group
- Shielding increases
- Attraction between outer electron and nucleus decreases
- So electron is more easily lost

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3
Q

What is the type of reaction between halide and concentrated H2SO4

A

Acid base reaction

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4
Q

What is the general formula for the reaction between halide ion and concentrated H2SO4

A

H2SO4 + NaX —> NaHSO4 + HX

Ionic equation:
(H+ + X - —> HX)

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5
Q

What is the observation when Br2 is formed

A

Brown/orange fumes

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6
Q

What is the observation when I2 is formed

A

Black solid/ Purple fumes

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7
Q

What is the observation when SO2 is formed

A

Pungent gas

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8
Q

What is the observation when S is formed

A

Yellow solid

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9
Q

What is the observation when H2S is formed

A

Smell of bad eggs

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10
Q

Describe the trend in electronegativity of halides

A

Decreases down the group

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11
Q

Explain the trend in electronegativity of halides

A

Decreases down the group

  • Atomic size increases
  • Shielding increases
    -Weaker attraction between nucleus and shared pair of e- of the covalent bond
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12
Q

State the trend in boiling point of the halides

A

Boiling point increases down the group

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13
Q

Explain the trend in boiling point of the halides

A

Boiling point increases down the group

  • Molecular size increases
  • Number of electrons increases
  • Van der waals forces between molecules increases
  • More energy required to overcome these forces
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14
Q

What is the best oxidising agent out of the halides

A

F2

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15
Q

What is the worst oxidising agent out of the halides

A

I2 (more shielding therefore worse at gaining an electron)

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16
Q

What is the best reducing agent out of the halide ions

A

I-

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17
Q

What is the worst reducing agent out of the halides

A

F-

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18
Q

What is observed when Cl2 is formed?

A

Green solution

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19
Q

What are the 4 main steps in testing for halide ions

A

1) Add HNO3
2) Add AgNO3
3) Add dilute NH3
4) Add concentrated NH3

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20
Q

Why do we add HNO3 (nitric acid) in the first step of identifying halide ions (why is silver nitrate acidified)
Write an equation for this reaction

A

Removes Co32- ions
(essential as Ag2CO3 is a white ppt)

2 HNO3 + Na2CO3 —> 2 NaNO3 + H2O + CO2

(Na is from compound like NaBr)

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21
Q

Which element is clearly identified after adding AgNO3 in the halide ion test

A

F-
(Gives a colourless solution)
(The others give white, cream and yellow)

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22
Q

Which element is clearly identified after adding DILUTE NH3 in the halide ion test. Write the equation for this reaction

A

Cl-
(In Cl- white ppt dissolves, Br- and I- have no visible change)

AgCl(s) + 2NH3(aq) —> [Ag(NH3)2]+(aq) + Cl- (aq)

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23
Q

Which element is clearly identified after adding CONCENTRATED NH3 in the halide ion test. Write the equation for this reaction

A

Br-
(In Br- cream ppt dissolves, I- has no visible change)

AgBr(s) + 2NH3(aq) —> [Ag(NH3)2]+ (aq) + Br - (aq)

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24
Q

What is the test for I- ions

A

No visible change after completing all 4 steps of halide ion test

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25
Q

What is the formula for the chlorate ion

A

ClO-

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26
Q

What is the equation for the reaction of chlorine and water without UV light, what type of reaction is this

A

Cl2 + H2O –>HCl + HClO (reversible)

Ionic:
Cl2 + H2O –> 2H+ + Cl- + ClO-
(Reversible)

Disproportionation reaction (Cl2 both oxidised and reduced)#

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27
Q

What is a disproportionation reaction?

A

One where the same species is both oxidised and reduced simultaneously

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28
Q

Why is the reaction of chlorine and water without UV a disproportionation reaction

A

Cl2 is both oxidised and reduced

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29
Q

Which species is oxidised and which species is reduced in the reaction of chlorine and water without UV

A

Cl2 is reduced and oxidised

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30
Q

What is the benefit of adding Cl2 to water

A

Cl2 kills microorganisms (useful in pools and drinking water)

31
Q

What is the risk of adding cl2 to water

A

Cl is toxic to humans in large amounts

32
Q

What is the equation for the reaction of Cl and water with UV (sunlight)

A

2Cl2 + 2H2O —> 4HCl + O2

Ionic:
2Cl2 + 2H2O —> 4H+ + 4Cl- + O2

(Green colour of Cl2 slowly fades as it reacts)

33
Q

Which species is oxidised and which species is reduced in the reaction of chlorine and water with UV

A

2Cl2 is Reduced

2H2O is Oxidised

34
Q

What is the chemical formula for bleach

A

Sodium Chlorate(I)

NaClO

35
Q

What is the equation for the manufacture of bleach
What is the colour change for this reaction

A

Cl2 + 2NaOH –> NaCl + NaClO + H2O

Ionic:
Cl2 + 2OH- —> Cl- + ClO- + H2O

Pale green to colourless

36
Q

Which species is oxidised and which is reduced in the reaction for the manufacture of bleach

A

Cl2 is oxidised and reduced

37
Q

What type of reaction is the manufacture of bleach

A

Disproportionation

38
Q

State the colours of precipitate formed when AgNO3 is added to Cl-,Br-, and I-
Write the ionic equation for each

A

Chloride (Cl-) ions: Produce a white precipitate of silver chloride
Ag+(aq) + Cl-(aq) –> AgCl(s)

Bromide (Br-) ions: Produce a cream precipitate of silver bromide
Ag+(aq) + Br-(aq) –> AgBr(s)

Iodide (I-) ions: Produce a yellow precipitate of silver iodide
Ag+(aq) + I-(aq) –> AgI(s)

39
Q

Identify all the reduction products formed when solid sodium iodide reacts with concentrated sulphuric acid.

A

SO2
S
H2S

40
Q

Write the 3 redox equations after the initial reaction between NaI and H2SO4

A

HI
The initial reaction is NaI (s) + H2SO4 (aq) → HI (g) + NaHSO4 (s)

I2
Concentrated sulfuric acid can oxidize HI to iodine (I2), which appears as a violet or purple vapor: 2HI (g) + H2SO4 (aq) → I2 (g) + SO2 (g) + 2H2O (l)

S
Concentrated sulfuric acid can oxidize HI to sulphur (S), which appears as a yellow solid: 6HI (g) + H2SO4 (aq) → 3I2 (g) + S (s) + 4H2O (l)

H2S
Concentrated sulfuric acid can oxidize HI to hydrogen sulphide (H2S), which has a strong odour of bad eggs: 8HI (g) + H2SO4 (aq) → 4I2 (g) + H2S (s) + 4H2O (l)

41
Q

What is the half equation for so42- to SO3

A

SO42- + 4H+ + 4e- —> SO3 + 2H2O

42
Q

What colour is F2, state a property of it

A

Very pale yellow gas
Highly reactive

43
Q

What colour is Cl2, state a property of it

A

Greenish, reactive gas, poisonous in high concentrations

44
Q

What colour is Br2, state a property of it

A

Brown-Orange liquid, gives off dense brown/orange poisonous fumes

45
Q

What colour is I2, state a property of it

A

Shiny grey solid, sublimes to purple gas

46
Q

What do more reactive halogens displace

A

Less reactive halide ions in a compound

47
Q

Will a halogen displace a less reactive halide ion in solution if the halide is lower in the periodic table

A

Yes

48
Q

What is the trend in oxidising ability of the halogens

A

Decreases down the group

49
Q

What is observed when a solution of KCl is added to a solution of chlorine

A

Very pale green solution, no reaction

50
Q

What is observed when a solution of KCl is added to a solution of bromine

A

Yellow-orange solution, no reaction

51
Q

What is observed when a solution of KCl is added to a solution of iodine

A

Brown solution, no reaction

52
Q

What colour is a test tube with chlorine present in solution

A

Very pale green solution (often colourless)

53
Q

What colour is a test tube with bromine present in solution

A

Yellow - orange solution

54
Q

What colour is a test tube with iodine present in solution

A

Brown solution (sometimes black solid present)

55
Q

What is observed when a solution of KBr is added to a solution of chlorine
Write the ionic equation for this reaction

A

Yellow-orange solution, Cl has displaced Br
Cl2(aq) + 2Br –(aq) –> 2Cl –(aq) + Br2(aq)

56
Q

What is observed when a solution of KBr is added to a solution of bromine

A

Yellow-orange solution, no reaction

57
Q

What is observed when a solution of KBr is added to a solution of iodine

A

Brown solution, no reaction

58
Q

What is observed when a solution of KI is added to a solution of chlorine
Write the ionic equation for this reaction

A

Brown solution, Cl has displaced I
Cl2(aq) + 2I–(aq) –> 2Cl –(aq) + I2(aq)

59
Q

What is observed when a solution of KI is added to a solution of bromine
Write the ionic equation for this reaction

A

Brown Solution, Br has displaced I
Br2(aq) + 2I–(aq) —> 2Br–(aq) + I2(aq)

60
Q

What is observed when a solution of KI is added to a solution of iodine

A

Brown Solution, no reaction

61
Q

What does the colour of a test tube after a halogen displacement reaction tell us

A

The colour of the solution in the test tube shows which free halogen is present in solution. (NOT HALIDE ION)

Chlorine =very pale green solution (often colourless),

Bromine = yellow-orange solution

Iodine = brown solution
(sometimes black solid
present)

62
Q

How do we make bleach

A

Reaction of chlorine with cold, dilute, aqueous NaOH

63
Q

Why does the Cl2 we add to swimming pools have to be replaced regularly

A

Sunlight can decompose chlorinated water, yet no ClO- is made which is what kills bacteria

64
Q

What are some uses of bleach

A

Cleaning products
Treating water

65
Q

Which out of these is an oxidising agent and which is a reducing agent:
Halogen and halide ion

A

Halogen - Oxidising agent
Halide ion - reducing agent

66
Q

Sketch the sable showing the products of the reaction between concentrated H2SO4 and Cl-, Br- and I-

A

NaF is the same as Cl

67
Q

What is the product with the lowest oxidation state of S that H2SO4 can be reduced to when reacting with Cl- (furthest product it can be oxidised to)

A

NaHSO4

68
Q

What is the product with the lowest oxidation state of S that H2SO4 can be reduced to when reacting with Br- (furthest product it can be oxidised to)

A

SO2

69
Q

What is the product with the lowest oxidation state of S that H2SO4 can be reduced to when reacting with I- (furthest product it can be oxidised to)

A

H2S

70
Q

What is the order of the possible products when halide ions react with concentrated H2SO4 in order from the highest oxidation state of S to the lowest

A

NaHSO4
SO2
S
H2S

71
Q

What happens to halide ions when they react with concentrated H2SO4

A

They are oxidised to give a halogen

72
Q

What is the observation when a hydrogen halide is produced
(HF, HCl, HBr, HI)

A

White steamy fumes evolved

73
Q

What do we get when we add add concentrated NH3 to any silver halide apart from AgI

A

Tollens
Halide ion

74
Q
A

Chemistry (Inorganic) (7 decks)

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